<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<script src="../js/jquery-1.11.0.min.js"></script>
<body>
	<input type="text" id="username" value="jack"/>
</body>
<script>
	//通过原生js
	//alert(document.getElementById("username").value)
	
	//通过jquery 获取jquery对象
	//var $username=$("#username");
	var $username=jQuery("#username");
	alert($username.val());
</script>
</html>